1. Field of the Invention
The present invention relates to a scroll compressor, and in particular to a scroll compressor suitable for a vapor compression refrigerating cycle that uses a refrigerant in the supercritical region of carbon dioxide (CO2), for example.
2. Description of the Related Art
Recently, a refrigeration cycle using carbon dioxide (referred to hereinbelow as a xe2x80x9ccarbon dioxide cyclexe2x80x9d) as a working gas (refrigerant gas) has been proposed, for example, in Japanese Examined Patent Application, Second Publication, No. Hei 7-18602, as one measure for eliminating the use of Freon (dichlorofluoromethane) as a refrigerant in the vapor compression-type refrigerating cycle. This carbon dioxide cycle is identical to the conventional vapor compression-type refrigerating cycle that uses Freon. That is, as shown by A-B-C-D-A in FIG. 8, which shows a carbon dioxide Mollier chart, the carbon dioxide in the gaseous phase is compressed by a compressor (A-B), and this gas-phase carbon dioxide that has been compressed to a high temperature is cooled in a radiator, such as a gas cooler (B-C). Next, the carbon dioxide is decompressed using a decompressor (C-D), the carbon dioxide that has changed to a liquid phase is vaporized (D-A), and an external fluid such as air is cooled by removing its latent heat of vaporization.
However, the critical temperature of carbon dioxide is about 31xc2x0, which is low compared to the critical temperature of Freon, the conventional refrigerant. When the external temperature is high, during summer, for example, the temperature of carbon dioxide on the radiator side is higher than its critical temperature. This means that the carbon dioxide does not condense at the radiator outlet side. In FIG. 8, this is shown by the fact that the line BC does not cross the saturated liquid line SL. In addition, the state on the radiator output side (point C) is determined by the discharge pressure of the compressor and the temperature of the carbon dioxide at the radiator outlet side. Moreover, the temperature of the carbon dioxide at the radiator outlet side is determined by the radiating capacity of the radiator and the temperature of the uncontrollable external air. Due to this, the temperature at the radiator outlet cannot be substantially controlled. Therefore, the state of the radiator outlet side (point C) can be controlled by the discharge pressure of the compressor, that is, the pressure on the radiator outlet side. This means that in order to guarantee sufficient refrigerating capacity (difference in enthalpy) when the temperature of the external air is high, during summer, for example, as shown by E-F-G-H-E, the pressure on the radiator output side must be high. In order to attain this, the operating pressure of the compressor must be high in comparison to the refrigeration cycle used with conventional Freon. In the case of an air conditioning device for an automobile, for example, the operating pressure of the compressor when using Freon (Trademark R134) is about 3 kg/cm2, while in contrast, this pressure must be raised to about 40 kg/cm2 for carbon dioxide. In addition, the operation stopping pressure when using Freon (Trademark R134) is about 15 kg/cm2, while in contrast it must be raised to about 100 kg/cm2 for carbon dioxide.
Below, for example, a common scroll compressor disclosed in Japanese Unexamined Patent Application, First Publication, No. Hei 4-234502, will be explained using FIG. 9. As shown in FIG. 9, in the casing 100, a fixed scroll member 101, an orbiting scroll member 102, and an Oldham ring 105, which is an anti-rotation device, are provided.
The fixed scroll member 101 is formed by a fixed side end plate 101a, an involute wrap 101b provided on one face of this fixed side end plate 101a, and a discharge port 104 provided approximately at the center part of this fixed end plate 101a. The orbiting scroll member 102 is formed by an orbiting side end plate 102a and an involute wrap 102b provided on one face of the orbiting side end plate 102a. This orbiting scroll member 102 is driven so as to revolve eccentrically with respect to the fixed scroll member 101. The orbiting scroll member 102 relatively rotating with respect to the fixed scroll member 101 forms an involute pressure chamber 103 between the involute wrap 102b of the orbiting scroll member 102 and the involute wrap 101b of the fixed scroll member 101. The Oldham ring 105 allows rotation of the orbiting scroll member 102 with respect to the fixed scroll member 101 while preventing autorotation of the orbiting scroll member 102. Furthermore, by adjusting the precision of the Oldham ring 105, the phase of the orbiting scroll member 102 and the fixed scroll member 101 can be adjusted.
However, in this conventional scroll compressor, the Oldham ring 105 is provided on the backside of the orbiting scroll member 102. Due to this, the position of the orbiting scroll member 102 is easily displaced with respect to the fixed scroll member 101, the phases of orbiting scroll member 102 and the fixed scroll member 101 easily shift, resulting in the problems that the assembly precision and the reliability are low.
In addition, for example, in a scroll compressor using carbon dioxide as the working gas and having a high operating pressure, when using an Oldham ring 105 having a long connection wrap 106, which is the part in contact with the fixed scroll member 101, an excessive load is applied to the base of the engagement projection 106, which causes fatigue damage, and thus, there is a concern that thereby the reliability will deteriorate.
In consideration of the above described problems with conventional technology, it is an object of the present invention to provide a scroll compressor that increases the assembly precision of the orbiting scroll member and the fixed scroll member, whose engagement projection is difficult to damage even when a large force is applied to the Oldham joint during operation, and therefore, has a high reliability.
According to a first aspect of the present invention, the present invention provides a scroll compressor furnished with a fixed scroll member including a first end plate and a first involute wrap provided on one face of the first end plate, the fixed scroll being movably supported in the axial direction of the fixed scroll member, and an orbiting scroll member including a second end plate and a second involute wrap provided on one face of the second end plate, which form a plurality of compression chambers in combination with the first involute wrap of the fixed scroll member, wherein a mechanism that prevents rotation of the orbiting scroll member with respect to the fixed scroll member is provided between the orbiting scroll member and the fixed scroll member.
The present invention also provides a scroll compressor including: a fixed scroll member comprising a first end plate and a first involute wrap provided on one face of the first end plate; a flat spring member disposed so as to support the fixed scroll member, the flat spring member allowing the fixed scroll member to move in the axial direction of the fixed scroll member; and an orbiting scroll member comprising a second end plate and a second involute wrap provided on one face of the second end plate, and which form a plurality of compression chambers in combination with the first involute wrap of the fixed scroll member, wherein a mechanism that prevents rotation of the orbiting scroll member with respect to the fixed scroll member is provided between the orbiting scroll member and the fixed scroll member.
According to this scroll compressor, because the mechanism that prevents the rotation of the orbiting scroll member with respect to the fixed scroll member is provided between the fixed scroll member and the orbiting scroll member, and the fixed scroll member is movably supported in the axial direction thereof, by placing the fixed scroll member and the orbiting scroll member each on the Oldham ring, the meshing of the fixed scroll member and the orbiting scroll member can be carried out with high precision. Also, the axial dimensions of the apparatus comprising the fixed scroll member, the orbiting scroll member, and the abovedescribed mechanism may be reduced in size.
In particular, a pair of first grooves are formed on the first end plate of the fixed scroll member and a pair of second grooves is formed on the second end plate of the orbiting scroll member, and the above-described mechanism is an Oldham ring comprising an annular body disposed rotatably between the fixed scroll member and the orbiting scroll member; first engaging projections that are provided on one end face of the annular body facing the fixed scroll member, the first engaging projections being engaged with the pair of the first grooves so as to prevent the rotation of the fixed scroll member with respect to the orbiting scroll member; and second engaging projections that are provided on the other end face of the annular body facing the orbiting scroll member, the second engaging projections being engaged with the pair of the second grooves so as to prevent the rotation of the orbiting scroll member with respect to the fixed scroll member.
In addition, the length of the first and second engaging projections formed on the Oldham ring are preferably substantially equal because then damage to the engaging projections due to fatigue will not occur easily even in the case that a large load is applied to the base of the engaging projections, as in a scroll compressor having a high operating pressure and using carbon dioxide as the working gas.
In addition, a concave part is preferably formed on a surface of the fixed scroll member and/or the orbiting scroll member facing the annular body, the concave part being used for embedding the annular body. This is because the axial dimensions of the apparatus comprising the fixed scroll member, the orbiting scroll member, and the above-described mechanism are then reduced in size.